1. Technical Field
The present disclosure relates to a generator of ultra wide band pulses. The present disclosure applies in particular, but not exclusively to wireless communications.
2. Description of the Related Art
Due to an increasing demand of wireless communications, new frequency bands are allocated to Ultra Wide Band (UWB) transmissions. The width of these frequency bands is such that it allows techniques of transmission by pulses to be implemented which make it possible to simplify the architecture of transmitters and receivers. Indeed, contrary to conventional wireless communications, transmissions by pulse do not require the implementation of functions of frequency synthesis and signal mixing which are demanding in terms of electrical consumption and surface of integrated circuit. However, Power Spectral Density (PSD) constraints have been defined to avoid interferences with other communication systems. In particular, the national commissions for the regulation of transmissions (Federal Communications Commission—FCC in the USA and ETSI—European Telecommunications Standards Institute in Europe) impose power spectral density masks for transmissions by radio pulses UWB-IR, which are implemented by a shaping of the transmitted pulses which is particularly delicate to implement.
To that end, it is known to make a ultra wide band pulse generator using passive circuits and transformers (cf. documents [1], [2] and [3]), or shaping analog filters (cf. document [4]), or Step Recovery diodes (SRD) (cf. document [5]). However, these circuits and components have the drawback of preventing a high integration rate, in particular due to the presence of inductances, or to the fact of not being able to be made in low cost standard CMOS technology, particularly due to the presence of SRD diodes. These techniques also have the drawback of generating only a preset pulse form which is not adaptable.
There are also techniques for generating variable pulses. To that end, it is known to use a local oscillator and a mixer to transpose different pulses produced in baseband, into different frequency bands (cf. documents [6], [7]). However this technique causes leaks and the amplitude of the pulses generated is limited. In addition, the electrical energy consumed by pulse in relation to the pulse amplitude is relatively high.
It has also been suggested to make totally digital pulse generators (cf. documents [8], [9], [10]). However, this solution leads to a frequency and amplitude limitation which depends of the circuit rapidity. Given the performances of the best current integrated circuits, this solution may not be considered to generate pulses of sufficient amplitude (>1 V) beyond 5 GHz.